Jun 10, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sat Jun 10 07:28:34 UTC 2017 (20170610 0730Z Day 3 shapefile | 20170610 0730Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170610 0730 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 120,012 549,537 Rapid City, SD...Gillette, WY...Sheridan, WY...Dickinson, ND...Scottsbluff, NE...
MARGINAL 290,851 10,334,916 Minneapolis, MN...St. Paul, MN...Sioux Falls, SD...Green Bay, WI...Rochester, MN...
Probabilistic Graphic
20170610 0730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 120,219 549,405 Rapid City, SD...Gillette, WY...Sheridan, WY...Dickinson, ND...Scottsbluff, NE...
5 % 289,782 10,308,464 Minneapolis, MN...St. Paul, MN...Sioux Falls, SD...Green Bay, WI...Rochester, MN...
   SPC AC 100728

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0228 AM CDT Sat Jun 10 2017

   Valid 121200Z - 131200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MONDAY AFTERNOON
   INTO MONDAY NIGHT NEAR THE LARAMIE AND BIG HORN MOUNTAINS INTO THE
   BLACK HILLS AND SURROUNDING AREAS OF THE NORTHERN PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING AREAS OF THE ROCKIES AND PLAINS INTO PORTIONS OF THE
   UPPER MIDWEST AND ADJACENT GREAT LAKES AREA...

   ...SUMMARY...
   Severe thunderstorms are possible from the vicinity of the Laramie
   and Big Horn mountains into the Black Hills, and surrounding areas
   of the northern Plains, Monday afternoon into Monday night.

   ...Discussion...
   Within the northern branch of split westerlies emanating from the
   mid-latitude Pacific, ridging appears likely to continue to build
   across and northeast of the Canadian Prairies.  To the south, the
   progressiveness of a deep closed low within the southern stream
   remains in some question, but guidance does continue to indicate at
   least slow movement/redevelopment northeastward across the Great
   Basin toward the northern Rockies during this period.  This is
   forecast to support a deepening area of low pressure across parts of
   eastern Montana and the Dakotas by late Monday night.  An initially
   stalled frontal zone across the north central Plains/Upper Midwest
   likely will shift northward toward the international border through
   the period, while a cold front advances east of the northern Rockies
   Monday night.

   Farther east, ridging within the southern stream appears likely to
   remain prominent across much of the eastern U.S., while a
   significant short wave continues to dig to the east of the northern
   stream ridging, southeast of Hudson bay into northern Quebec.  The
   primary associated cold front is expected to remain well to the
   north of the international border area through this period, but a
   preceding influx of cooler air may advance into parts of upstate New
   York and northern New England late Monday night.

   ...Northern Rockies/Plains...
   The mid-level cold core of the closed low, and the core of the
   stronger associated mid/upper jet, may remain largely displaced to
   the west of the region through much of this period.  However,
   pronounced veering of wind fields with height, from low-level
   easterlies to  modest southerly mid-level flow (on the order of
   30-40+ kt) is expected to contribute to sufficient shear for
   organized convective development.  This will occur as moistening
   within the low-level easterlies, beneath steep lower/mid
   tropospheric lapse rates, contributes to appreciable CAPE on the
   order of 1000-2000 J/kg.

   Orographic forcing near/east of the Laramie and Big Horn mountains
   may support initiation of storms, before activity increases further
   in the presence of increasing  synoptic forcing for upward vertical
   motion (associated with strengthening warm advection beneath
   divergent upper flow, downstream of the closed low) by Monday
   afternoon.  This environment is expected to be conducive to
   supercells, then perhaps considerable upscale convective growth into
   one or two organizing clusters spreading across the Black Hills and
   adjacent areas of the northern Plains by Monday night.

   ...Upper Mississippi Valley/adjacent Great Lakes...
   Coverage of potential storm development remains more unclear than
   across the northern high Plains region, but the environment may be
   conducive to isolated/widely scattered strong to severe storm
   development within a zone of warm advection along/north of the
   retreating frontal zone Monday into Monday night.

   ..Kerr.. 06/10/2017

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